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CHAPTER 4 PORT FUNCTIONS
User’s Manual U15798EJ2V0UD
(3) Memory expansion mode register (MEM)
This register is used to set whether port 4 is used as port pins or key input pins.
MEM is set by a 1-bit or 8-bit memory manipulation instruction.
RESET input sets the value of this register to 00H.
Figure 4-20. Format of Memory Expansion Mode Register (MEM)
MM2
MM1
MM0
Single-chip/key return mode selection
0
0
0
Single-chip mode (used as port pin)
0
0
1
Key return mode (used as key input pin)
Other than above
Setting prohibited
Caution Be sure to set MM1 and MM2 to 0.
7
0
Symbol
MEM
6
0
5
0
4
0
3
0
2
MM2
1
MM1
0
MM0
Address: FF47H After reset: 00H R/W
